The present invention relates to a method for preparing a fluorine-containing alcohol compound and a catalyst used in the preparation method.
Japanese Unexamined Patent Publication No. 1992-506507 suggests a method for preparing a fluorine-containing alcohol having water repellency and oil repellency by treating a halogenated alkyl on a catalyst to convert it into an alcohol. However, this method has the shortcomings of using a gas phase reaction at a temperature as high as 400 to 600xc2x0 C. and of a low degree of conversion and selectivity.
A primary object of the present invention is to provide a method for preparing a fluorine-containing alcohol compound without using unusual reagents or solvents under relatively moderate reaction conditions and in a high yield.
The inventors of the present invention conducted extensive research to achieve the above object. Consequently, they found that a fluorine-containing alcohol compound can be prepared at a relatively low reaction temperature and in a high yield by using a catalyst which has an element of a specific group of the periodic table, an ion of such an element, an oxide, hydroxide, salt or the like containing such element(s) supported on a specific complex oxide. The present invention was accomplished based on this finding.
Specifically, the present invention provides the following catalyst for preparing a fluorine-containing alcohol compound and a method for preparing a fluorine-containing alcohol compound.
1. A catalyst for preparing a fluorine-containing alcohol compound, the catalyst having at least one component selected from
(i) at least one element selected from the elements in Group 1B, Group 2B, Group 6A, Group 7A and Group 8 of the periodic table,
(ii) at least one ion of the element of the above (i),
(iii) at least one oxide containing one or more elements of the above (i),
(iv) at least one hydroxide containing one or more elements of the above (i), and
(v) at least one salt containing one or more elements of the above (i),
said component being supported on at least one complex oxide selected from Sixe2x80x94Al complex oxides, Alxe2x80x94P complex oxides and Sixe2x80x94Alxe2x80x94P complex oxides.
2. The catalyst according to item 1 in which the complex oxide is an oxide having a zeolite structure.
3. The catalyst according to item 1 or 2, wherein the component supported on the complex oxide is at least one component selected from ions of elements selected from Cu, Ag, Ni, Co, Fe, Hg and Pd, oxides containing such element(s), hydroxides containing such element(s) and salts containing such element(s).
4. A method for preparing a fluorine-containing alcohol compound represented by formula (II):
Rfxe2x80x94(CH2)nOHxe2x80x83xe2x80x83(II)
wherein Rf represents a perfluoroalkyl group or a polyfluoroalkyl group and n is an integer from 1 to 5,
the method comprising the step of reacting water with a halogenated fluorine compound represented by formula (I):
Rfxe2x80x94(CH2)nXxe2x80x83xe2x80x83(I)
wherein Rf is as defined in the above, X represents I, Br or Cl and n is as defined in the above, in the presence of the catalyst as defined in any one of the above items 1 to 3.
5. The method according to item 4, wherein the reaction between the halogenated fluorine compound and water is carried out in an atmosphere of an oxygen-containing gas.
6. The method according to item 4 or 5, wherein the reaction is carried out under increased pressure.
7. The method for preparing a fluorine-containing alcohol compound according to item 5, wherein X in formula (I) is I, the method further comprising the step of recovering I2 produced as a byproduct.
The catalyst for preparing a fluorine-containing alcohol compound for use in the present invention has at least one component selected from
(i) at least one element selected from the elements in Group 1B, Group 2B, Group 6A, Group 7A and Group 8 of the periodic table,
(ii) at least one ion of the element of the above (i),
(iii) at least one oxide containing one or more elements of the above (i),
(iv) at least one hydroxide containing one or more elements of the above (i), and
(v) at least one salt containing one or more elements of the above (i),
said component being supported on at least one complex oxide selected from Sixe2x80x94Al complex oxides, Alxe2x80x94P complex oxides and Sixe2x80x94Alxe2x80x94P complex oxides.
Among these elements, examples of the elements in Group 1B include Cu, Ag and Au, among others; examples of the elements in Group 2B include Zn, Cd and Hg, among others; examples of the elements in Group 6A include Cr, Mo and W, among others; examples of the elements in Group 7A include Mn, Tc and Re, among others; examples of the elements in Group 8 include Ni, Co, Fe, Ru, Rh, Pd, Pt and Ir, among others. These elements may be used singly or in combinations of two or more species.
In the present invention, these elements may be supported, and the ions of these elements, oxides, hydroxides, salts or the like containing one or more of these elements may be also supported. Hereinafter in the present specification, these components may be collectively referred to as active components.
Among the active components, the oxides may be those containing one or more of the above elements, and the valence of the element is not restricted. The hydroxides may be those containing one or more of the above elements, and the valence of the element is not restricted. The ions may be those of the above elements, and the charge number of the ion is not restricted. Examples of the useful salts include sulfates, nitrates, carbonates and the like.
The above-mentioned active components may be used singly or in combinations of two or more species.
Among the above-mentioned active components, preferable are ions of Cu, Ag, Ni, Co, Fe, Hg, Pd and other elements, oxides containing one or more of these elements, hydroxides containing one or more of these elements, salts containing one or more of these elements, etc. The catalyst which uses the active component containing Cu, Ni or the like has high selectivity for the desired product; the catalyst using active component containing Ag allows a reaction at a relatively low temperature; and the catalyst using active component containing Fe exhibits good catalytic activity.
The catalyst of the present invention uses at least one complex oxide selected from Sixe2x80x94Al complex oxides, Alxe2x80x94P complex oxides and Sixe2x80x94Alxe2x80x94P complex oxides as a carrier to support the above-mentioned active component.
Examples of such complex oxides include silica-alumina, synthetic silica-alumina zeolite, natural silica-alumina zeolite, aluminum phosphate, synthetic aluminum phosphate zeolite, synthetic Sixe2x80x94Alxe2x80x94P zeolite (SAPO) and the like.
Using a catalyst having the above-mentioned component supported on at least one complex oxide selected from Sixe2x80x94Al complex oxides, Alxe2x80x94P complex oxides and Sixe2x80x94Alxe2x80x94P complex oxides can improve the degree of conversion of raw material, selectivity of the desired product, etc. in the below-mentioned method for preparing a fluorine-containing alcohol compound. Among these complex oxides, using an oxide having a zeolite structure particularly increases selectivity of alcohol.
The method to support the above active component on the complex oxide is not particularly limited, and may be suitably selected from various conventional support methods depending on the kind of the component to be supported. For example, the sol-gel method, hydrothermal synthesis, impregnation method, co-precipitation method, CVD method (chemical vapor deposition method), ion-implantation method or any other methods may be employed.
For instance, when using SAPO-11 zeolite as a Sixe2x80x94Alxe2x80x94P complex oxide, the above-mentioned active component can be supported on the complex oxide by immersing the zeolite in a solution of a soluble metal compound (e.g., an aqueous solution of copper sulfate or like metal salt) to impregnate the zeolite with the solution, optionally followed by heating. The forms of the complex oxide when immersed in a metal compound solution include, but are not limited to, powders, granules, tablets, honeycombs, among others.
In a catalyst comprising a complex oxide which has the above component supported thereon, the amount of the active component, calculated as the metal oxide, per the total catalyst is suitably about 1 to 30% by weight, preferably about 5 to 15% by weight.
Next, the method for preparing a fluorine-containing alcohol compound using the above-mentioned catalyst will be explained.
In the method of the present invention, in the presence of the above-mentioned catalyst, a fluorine-containing alcohol compound represented by formula (II)
Rfxe2x80x94(CH2)nOHxe2x80x83xe2x80x83(II)
wherein Rf represents a perfluoroalkyl group or a polyfluoroalkyl group and n is an integer from 1 to 5 can be prepared by reacting water with a halogenated fluorine compound represented by formula (I):
Rfxe2x80x94(CH2)nXxe2x80x83xe2x80x83(I)
wherein Rf and n are as defined above and X represents I, Br or Cl.
In the compound of formula (I), examples of the perfluoroalkyl group represented by Rf include C1-C20 straight-chain or branched-chain perfluoroalkyl groups. Specific examples include CF3, C2F5, (n- or iso)C3F7, (n-, iso, sec- or tert-)C4F9, CF3 (CF2)m- (m is an integer from 4 to 19), among others.
Examples of the polyfluoroalkyl group include HCF2 (CF2)p- (p is an integer from 1 to 19), among others.
The reaction between the halogenated fluorine compound represented by formula (I) and water can be carried out by a batch method or a continuous method. The reactor for this reaction is not particularly restricted, and a gas phase continuous reactor equipped with reaction vessel such as fixed bed, fluidized bed, moving bed, etc., or a batch reactor may be used.
The method for reacting the halogenated fluorine compound and water by gas phase continuous reaction comprises, for example, the steps of placing a stainless-steel reaction tube filled with the catalyst of the present invention in an electric heating furnace, heating the catalyst layer to a reaction temperature, introducing the raw material and water into a vaporizer at a constant rate using a plunger pump or the like, conveying the vaporized gas to the catalyst layer by air or like carrier gases to react the vaporized gas, and recovering a reaction product with a subsequent trap or the like. Although favorable reaction conditions may somewhat vary depending on the kind of catalyst used, the reaction temperature may be about 120xc2x0 C. to 400xc2x0 C., preferably about 150xc2x0 C. to 300xc2x0 C. The reaction can be carried out under atmospheric pressure or increased pressure. Particularly, when reacting under increased pressure, preferably under absolute pressure of 0.294 MPa or higher, more preferably 0.392 MPa or higher, even more preferably 0.49 MPa or higher, particularly preferably 0.588 Mpa or higher, alcohol selectivity can be increased. The molar ratio of the halogenated fluorine compound to water is desirably about 1:0.2-1:200. W/F (contact time) may be about 0.1 to 10 gxc2x7sec/ml.
When the reaction is conducted by the batch method, it can be conducted, for example, by the method comprising the following steps: placing the raw material, water and the catalyst in an autoclave or like pressure vessel; and heating the mixture with a heater to a reaction temperature to allow the mixture to react for a certain period of time with stirring. Although preferable reaction conditions may somewhat vary depending on the kind of catalyst used, the reaction temperature may be about 120xc2x0 C. to 400xc2x0 C., preferably about 150xc2x0 C. to 300xc2x0 C. The molar ratio of the halogenated fluorine compound to water is desirably about 1:0.2-1:200. The weight ratio of the halogenated fluorine compound to the catalyst may be about 1:0.01-1:1. The reaction time may be about an hour to 100 hours.
As for the reaction atmosphere, the reaction may be conducted in an atmosphere including nitrogen, helium, carbon dioxide or like inert gases, air or like oxygen-containing gases, oxygen-containing gas diluted with an inert gas, among others. In particular, conducting reaction in an atmosphere of air or like oxygen-containing gas accelerates the oxidation of HX formed by the reaction and formation of X2, thereby facilitating the recovery of X2. The recovered X2 is useful as a raw material in the production process of the starting compound represented by the above formula (I): Rfxe2x80x94(CH2)nX. Particularly when the formed X2 is I2, iodine can be advantageously recovered without troublesome and environmentally unfavorable treatments such as oxidation by chlorine which is conventionally necessary for recovering iodine from a waste liquid containing iodide ions. The thus recovered iodine is a very important resource which can be collected by distillation, sublimation or other methods. Such iodine can be used as a raw material for preparing the staring compound for use in the method of the present invention, i.e., halogenated fluorine compound.
In the continuous reaction, the supply of air and like oxygen-containing gas together with the raw material and water can prevent catalyst activity from decreasing. In this case, the amount of oxygen is preferably at least about xc2xc mole per mole of the halogenated fluorine compound.
According to the preparation method of the present invention, by reacting water and the halogenated fluorine compound in the presence of the specific catalyst, the fluorine-containing alcohol compound can be prepared at a relatively low reaction temperature and in a high yield.